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	<title>findIndex</title>
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	<div>用于找出第一个符合条件的数组成员的位置，如果没有找到返回-1</div>
	<script type="text/javascript">
		let arr = [1,5,10,15]
		console.log(arr.findIndex((value,index)=>value>9 ))
		console.log(arr.findIndex(item => item==5))
		console.log(arr.findIndex(item => item==16))
	</script>
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